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Chiarelli DP, Sharma BD, Hon S, Bergamo LW, Lynd LR, Olson DG. Expression and characterization of monofunctional alcohol dehydrogenase enzymes in Clostridium thermocellum. Metab Eng Commun 2024; 19:e00243. [PMID: 39040142 PMCID: PMC11260334 DOI: 10.1016/j.mec.2024.e00243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2024] [Revised: 06/17/2024] [Accepted: 06/18/2024] [Indexed: 07/24/2024] Open
Abstract
Clostridium thermocellum is a thermophilic anaerobic bacterium that could be used for cellulosic biofuel production due to its strong native ability to consume cellulose, however its ethanol production ability needs to be improved to enable commercial application. In our previous strain engineering work, we observed a spontaneous mutation in the native adhE gene that reduced ethanol production. Here we attempted to complement this mutation by heterologous expression of 18 different alcohol dehydrogenase (adh) genes. We were able to express all of them successfully in C. thermocellum. Surprisingly, however, none of them increased ethanol production, and several actually decreased it. Our findings contribute to understanding the correlation between C. thermocellum ethanol production and Adh enzyme cofactor preferences. The identification of a set of adh genes that can be successfully expressed in this organism provides a foundation for future investigations into how the properties of Adh enzymes affect ethanol production.
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Affiliation(s)
- Daniela Prates Chiarelli
- Centro de Biologia Molecular e Engenharia Genética (CBMEG), Universidade Estadual de Campinas (UNICAMP), Campinas, SP, Brazil
- Programa de Pós-Graduação Em Genética e Biologia Molecular, Instituto de Biologia (IB), Universidade Estadual de Campinas (UNICAMP), Campinas, SP, Brazil
| | - Bishal Dev Sharma
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA
- Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Shuen Hon
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA
- Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Luana Walravens Bergamo
- Centro de Biologia Molecular e Engenharia Genética (CBMEG), Universidade Estadual de Campinas (UNICAMP), Campinas, SP, Brazil
- Programa de Pós-Graduação Em Genética e Biologia Molecular, Instituto de Biologia (IB), Universidade Estadual de Campinas (UNICAMP), Campinas, SP, Brazil
| | - Lee R. Lynd
- Centro de Biologia Molecular e Engenharia Genética (CBMEG), Universidade Estadual de Campinas (UNICAMP), Campinas, SP, Brazil
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA
- Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Daniel G. Olson
- Centro de Biologia Molecular e Engenharia Genética (CBMEG), Universidade Estadual de Campinas (UNICAMP), Campinas, SP, Brazil
- Thayer School of Engineering, Dartmouth College, Hanover, NH, USA
- Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, USA
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Ponsetto P, Sasal EM, Mazzoli R, Valetti F, Gilardi G. The potential of native and engineered Clostridia for biomass biorefining. Front Bioeng Biotechnol 2024; 12:1423935. [PMID: 39219620 PMCID: PMC11365079 DOI: 10.3389/fbioe.2024.1423935] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2024] [Accepted: 08/06/2024] [Indexed: 09/04/2024] Open
Abstract
Since their first industrial application in the acetone-butanol-ethanol (ABE) fermentation in the early 1900s, Clostridia have found large application in biomass biorefining. Overall, their fermentation products include organic acids (e.g., acetate, butyrate, lactate), short chain alcohols (e.g., ethanol, n-butanol, isobutanol), diols (e.g., 1,2-propanediol, 1,3-propanediol) and H2 which have several applications such as fuels, building block chemicals, solvents, food and cosmetic additives. Advantageously, several clostridial strains are able to use cheap feedstocks such as lignocellulosic biomass, food waste, glycerol or C1-gases (CO2, CO) which confer them additional potential as key players for the development of processes less dependent from fossil fuels and with reduced greenhouse gas emissions. The present review aims to provide a survey of research progress aimed at developing Clostridium-mediated biomass fermentation processes, especially as regards strain improvement by metabolic engineering.
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Affiliation(s)
| | | | - Roberto Mazzoli
- Structural and Functional Biochemistry, Laboratory of Proteomics and Metabolic Engineering of Prokaryotes, Department of Life Sciences and Systems Biology, University of Torino, Torino, Italy
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3
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Zhang JZ, Li YZ, Xi ZN, Gao HP, Zhang Q, Liu LC, Li FL, Ma XQ. Engineered acetogenic bacteria as microbial cell factory for diversified biochemicals. Front Bioeng Biotechnol 2024; 12:1395540. [PMID: 39055341 PMCID: PMC11269201 DOI: 10.3389/fbioe.2024.1395540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2024] [Accepted: 06/28/2024] [Indexed: 07/27/2024] Open
Abstract
Acetogenic bacteria (acetogens) are a class of microorganisms with conserved Wood-Ljungdahl pathway that can utilize CO and CO2/H2 as carbon source for autotrophic growth and convert these substrates to acetate and ethanol. Acetogens have great potential for the sustainable production of biofuels and bulk biochemicals using C1 gases (CO and CO2) from industrial syngas and waste gases, which play an important role in achieving carbon neutrality. In recent years, with the development and improvement of gene editing methods, the metabolic engineering of acetogens is making rapid progress. With introduction of heterogeneous metabolic pathways, acetogens can improve the production capacity of native products or obtain the ability to synthesize non-native products. This paper reviews the recent application of metabolic engineering in acetogens. In addition, the challenges of metabolic engineering in acetogens are indicated, and strategies to address these challenges are also discussed.
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Affiliation(s)
- Jun-Zhe Zhang
- Qingdao C1 Refinery Engineering Research Center, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Yu-Zhen Li
- Qingdao C1 Refinery Engineering Research Center, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Zhi-Ning Xi
- Qingdao C1 Refinery Engineering Research Center, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, China
| | - Hui-Peng Gao
- Sinopec Dalian (Fushun) Research Institute of Petroleum and Petrochemicals, Dalian, China
| | - Quan Zhang
- Sinopec Dalian (Fushun) Research Institute of Petroleum and Petrochemicals, Dalian, China
| | - Li-Cheng Liu
- Key Laboratory of Marine Chemistry Theory and Technology (Ministry of Education), College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao, China
| | - Fu-Li Li
- Qingdao C1 Refinery Engineering Research Center, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, China
- Shandong Energy Institute, Qingdao, China
- Qingdao New Energy Shandong Laboratory, Qingdao, China
| | - Xiao-Qing Ma
- Qingdao C1 Refinery Engineering Research Center, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, China
- Qingdao New Energy Shandong Laboratory, Qingdao, China
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4
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He L, Xiao F, Dou CX, Zhou B, Chen ZH, Wang JY, Wang CG, Xie F. Integrated Comparative Transcriptome and Weighted Gene Co-Expression Network Analysis Provide Valuable Insights into the Mechanisms of Pinhead Initiation in Chinese Caterpillar Mushroom Ophiocordyceps sinensis (Ascomycota). Int J Med Mushrooms 2024; 26:41-54. [PMID: 39171630 DOI: 10.1615/intjmedmushrooms.2024054674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/23/2024]
Abstract
The initiation and formation of the "pinhead" is the key node in growth process of Ophiocordyceps sinensis (Chinese Cordyceps). The research on the mechanism of changes in this growth stage is the basis for realizing the industrialization of its artificial cultivation. Clarifying the mechanisms of pinhead initiation is essential for its further application. Here, we performed a comprehensive transcriptome analysis of pinhead initiation process in O. sinensis. Comparative transcriptome analysis revealed remarkable variation in gene expression and enriched pathways at different pinhead initiation stages. Gene co-expression network analysis by WGCNA identified 4 modules highly relevant to different pinhead initiation stages, and 23 hub genes. The biological function analysis and hub gene annotation of these identified modules demonstrated that transmembrane transport and nucleotide excision repair were the topmost enriched in pre-pinhead initiation stage, carbohydrate metabolism and protein glycosylation were specially enriched in pinhead initiation stage, nucleotide binding and DNA metabolic process were over-represented after pinhead stage. These key regulators are mainly involved in carbohydrate metabolism, synthesis of proteins and nucleic acids. This work excavated the candidate pathways and hub genes related to the pinhead initiation stage, which will serve as a reference for realizing the industrialization of artificial cultivation in O. sinensis.
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Affiliation(s)
- Li He
- School of Biological and Pharmaceutical Engineering, Lanzhou Jiaotong University, Lanzhou, GanSu, P.R. China
| | - Fan Xiao
- School of Biological and Pharmaceutical Engineering, Lanzhou Jiaotong University, Lanzhou, GanSu, P.R. China
| | - Chen Xi Dou
- School of Biological and Pharmaceutical Engineering, Lanzhou Jiaotong University, Lanzhou, GanSu, P.R. China
| | - Bo Zhou
- School of Biological and Pharmaceutical Engineering, Lanzhou Jiaotong University, Lanzhou, GanSu, P.R. China
| | - Zhao He Chen
- School of Biological and Pharmaceutical Engineering, Lanzhou Jiaotong University, Lanzhou, GanSu, P.R. China
| | - Jing Yi Wang
- School of Biological and Pharmaceutical Engineering, Lanzhou Jiaotong University, Lanzhou, GanSu, P.R. China
| | - Cheng Gang Wang
- School of Biological and Pharmaceutical Engineering, Lanzhou Jiaotong University, Lanzhou, GanSu, P.R. China
| | - Fang Xie
- School of Biological and Pharmaceutical Engineering, Lanzhou Jiaotong University, Lanzhou, GanSu, P.R. China
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5
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Seo H, Singh P, Wyman CE, Cai CM, Trinh CT. Rewiring metabolism of Clostridium thermocellum for consolidated bioprocessing of lignocellulosic biomass poplar to produce short-chain esters. BIORESOURCE TECHNOLOGY 2023:129263. [PMID: 37271458 DOI: 10.1016/j.biortech.2023.129263] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Revised: 05/29/2023] [Accepted: 05/30/2023] [Indexed: 06/06/2023]
Abstract
Consolidated bioprocessing (CBP) of lignocellulosic biomass uses cellulolytic microorganisms to enable enzyme production, saccharification, and fermentation to produce biofuels, biochemicals, and biomaterials in a single step. However, understanding and redirecting metabolisms of these microorganisms compatible with CBP are limited. Here, a cellulolytic thermophile Clostridium thermocellum was engineered and demonstrated to be compatible with CBP integrated with a Co-solvent Enhanced Lignocellulosic Fractionation (CELF) pretreatment for conversion of hardwood poplar into short-chain esters with industrial use as solvents, flavors, fragrances, and biofuels. The recombinant C. thermocellum engineered with deletion of carbohydrate esterases and stable overexpression of alcohol acetyltransferases improved ester production without compromised deacetylation activities. These esterases were discovered to exhibit promiscuous thioesterase activities and their deletion enhanced ester production by rerouting the electron and carbon metabolism. Ester production was further improved up to 80-fold and ester composition could be modulated by deleting lactate biosynthesis and using poplar with different pretreatment severity.
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Affiliation(s)
- Hyeongmin Seo
- Department of Chemical and Biomolecular Engineering, The University of Tennessee, Knoxville, TN, USA; Center of Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Priyanka Singh
- Center of Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, USA; Chemical and Environmental Engineering Department, University of California, Riverside, CA 92521, USA
| | - Charles E Wyman
- Center of Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, USA; Chemical and Environmental Engineering Department, University of California, Riverside, CA 92521, USA
| | - Charles M Cai
- Center of Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, USA; Chemical and Environmental Engineering Department, University of California, Riverside, CA 92521, USA
| | - Cong T Trinh
- Department of Chemical and Biomolecular Engineering, The University of Tennessee, Knoxville, TN, USA; Center of Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
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6
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The Roles of Nicotinamide Adenine Dinucleotide Phosphate Reoxidation and Ammonium Assimilation in the Secretion of Amino Acids as Byproducts of Clostridium thermocellum. Appl Environ Microbiol 2023; 89:e0175322. [PMID: 36625594 PMCID: PMC9888227 DOI: 10.1128/aem.01753-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Clostridium thermocellum is a cellulolytic thermophile that is considered for the consolidated bioprocessing of lignocellulose to ethanol. Improvements in ethanol yield are required for industrial implementation, but the incompletely understood causes of amino acid secretion impede progress. In this study, amino acid secretion was investigated via gene deletions in ammonium-regulated, nicotinamide adenine dinucleotide phosphate (NADPH)-supplying and NADPH-consuming pathways as well as via physiological characterization in cellobiose-limited or ammonium-limited chemostats. First, the contribution of the NADPH-supplying malate shunt was studied with strains using either the NADPH-yielding malate shunt (Δppdk) or a redox-independent conversion of PEP to pyruvate (Δppdk ΔmalE::Peno-pyk). In the latter, branched-chain amino acids, especially valine, were significantly reduced, whereas the ethanol yield increased from 46 to 60%, suggesting that the secretion of these amino acids balances the NADPH surplus from the malate shunt. The unchanged amino acid secretion in Δppdk falsified a previous hypothesis on an ammonium-regulated PEP-to-pyruvate flux redistribution. The possible involvement of another NADPH-supplier, namely, NADH-dependent reduced ferredoxin:NADP+ oxidoreductase (nfnAB), was also excluded. Finally, the deletion of glutamate synthase (gogat) in ammonium assimilation resulted in the upregulation of NADPH-linked glutamate dehydrogenase activity and decreased amino acid yields. Since gogat in C. thermocellum is putatively annotated as ferredoxin-linked, a claim which is supported by the product redistribution observed in this study, this deletion likely replaced ferredoxin with NADPH in ammonium assimilation. Overall, these findings indicate that a need to reoxidize NADPH is driving the observed amino acid secretion, likely at the expense of the NADH needed for ethanol formation. This suggests that metabolic engineering strategies that simplify the redox metabolism and ammonium assimilation can contribute to increased ethanol yields. IMPORTANCE Improving the ethanol yield of C. thermocellum is important for the industrial implementation of this microorganism in consolidated bioprocessing. A central role of NADPH in driving amino acid byproduct formation was demonstrated by eliminating the NADPH-supplying malate shunt and separately by changing the cofactor specificity in ammonium assimilation. With amino acid secretion diverting carbon and electrons away from ethanol, these insights are important for further metabolic engineering to reach industrial requirements on ethanol yield. This study also provides chemostat data that are relevant for training genome-scale metabolic models and for improving the validity of their predictions, especially considering the reduced degree-of-freedom in the redox metabolism of the strains generated here. In addition, this study advances the fundamental understanding on the mechanisms underlying amino acid secretion in cellulolytic Clostridia as well as on the regulation and cofactor specificity in ammonium assimilation. Together, these efforts aid in the development of C. thermocellum for the sustainable consolidated bioprocessing of lignocellulose to ethanol with minimal pretreatment.
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Mao Q, Jiang J, Wu X, Ma Y, Zhang Y, Zhao Y, Zhang Y, Wang Q. Bifunctional alcohol/aldehyde dehydrogenase AdhE controls phospho-transferase system sugar utilization and virulence gene expression by interacting PtsH in Edwardsiella piscicida. Microbiol Res 2022; 260:127018. [DOI: 10.1016/j.micres.2022.127018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Revised: 03/26/2022] [Accepted: 03/29/2022] [Indexed: 10/18/2022]
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Le Y, Sun J. CRISPR/Cas genome editing systems in thermophiles: Current status, associated challenges, and future perspectives. ADVANCES IN APPLIED MICROBIOLOGY 2022; 118:1-30. [PMID: 35461662 DOI: 10.1016/bs.aambs.2022.02.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Thermophiles, offering an attractive and unique platform for a broad range of applications in biofuels and environment protections, have received a significant attention and growing interest from academy and industry. However, the exploration and exploitation of thermophilic organisms have been hampered by the lack of a powerful genome manipulation tool to improve production efficiency. At current, the clustered Regularly Interspaced Short Palindromic Repeat (CRISPR)/CRISPR associated (Cas) system has been successfully exploited as a competent, simplistic, and powerful tool for genome engineering both in eukaryotes and prokaryotes. Indeed, with the significant efforts made in recent years, some thermostable Cas9 proteins have been well identified and characterized and further, some thermostable Cas9-based editing tools have been successfully established in some representative obligate thermophiles. In this regard, we reviewed the current status and its progress in CRISPR/Cas-based genome editing system towards a variety of thermophilic organisms. Despite the potentials of these progresses, multiple factors/barriers still have to be overcome and optimized for improving its editing efficiency in thermophiles. Some insights into the roles of thermostable CRISPR/Cas technologies for the metabolic engineering of thermophiles as a thermophilic microbial cell factory were also fully analyzed and discussed.
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Affiliation(s)
- Yilin Le
- Biofuels institute, School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang, Jiangsu, PR China.
| | - Jianzhong Sun
- Biofuels institute, School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang, Jiangsu, PR China.
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Bao W, He Y, Liu W. Diversity Analysis of Bacterial and Function Prediction in Hurunge From Mongolia. Front Nutr 2022; 9:835123. [PMID: 35399660 PMCID: PMC8990233 DOI: 10.3389/fnut.2022.835123] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Accepted: 01/19/2022] [Indexed: 11/13/2022] Open
Abstract
With the continuous infiltration of industrialization and modern lifestyle into pastoral areas, the types and processing capacity of Hurunge are decreasing, and the beneficial microbial resources contained in it are gradually disappearing. The preservation and processing of Hurunge are very important for herdsmen to successfully produce high-quality koumiss in the second year. Therefore, in this study, 12 precious Hurunge samples collected from Bulgan Province, Ovorkhangay Province, Arkhangay Province, and Tov Province of Mongolia were sequenced based on the V3-V4 region of the 16S rRNA gene, and the bacterial diversity and function were predicted and analyzed. There were significant differences in the species and abundance of bacteria in Hurunge from different regions and different production methods (p < 0.05). Compared with the traditional fermentation methods, the OTU level of Hurunge fermented in the capsule was low, the Acetobacter content was high and the bacterial diversity was low. Firmicutes and Lactobacillus were the dominant phylum and genus of 12 samples, respectively. The sample QHA contained Komagataeibacter with the potential ability to produce bacterial nanocellulose, and the abundance of Lactococcus in the Tov Province (Z) was significantly higher than that in the other three regions. Functional prediction analysis showed that genes related to the metabolism of bacterial growth and reproduction, especially carbohydrate and amino acid metabolism, played a dominant role in microorganisms. In summary, it is of great significance to further explore the bacterial diversity of Hurunge for the future development and research of beneficial microbial resources, promotion, and protection of the traditional ethnic dairy products.
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Affiliation(s)
- Wuyundalai Bao
- College of Food Science and Engineering, Inner Mongolia Agricultural University, Hohhot, China
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Assessing the impact of substrate-level enzyme regulations limiting ethanol titer in Clostridium thermocellum using a core kinetic model. Metab Eng 2022; 69:286-301. [PMID: 34982997 DOI: 10.1016/j.ymben.2021.12.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 12/16/2021] [Accepted: 12/29/2021] [Indexed: 11/20/2022]
Abstract
Clostridium thermocellum is a promising candidate for consolidated bioprocessing because it can directly ferment cellulose to ethanol. Despite significant efforts, achieved yields and titers fall below industrially relevant targets. This implies that there still exist unknown enzymatic, regulatory, and/or possibly thermodynamic bottlenecks that can throttle back metabolic flow. By (i) elucidating internal metabolic fluxes in wild-type C. thermocellum grown on cellobiose via 13C-metabolic flux analysis (13C-MFA), (ii) parameterizing a core kinetic model, and (iii) subsequently deploying an ensemble-docking workflow for discovering substrate-level regulations, this paper aims to reveal some of these factors and expand our knowledgebase governing C. thermocellum metabolism. Generated 13C labeling data were used with 13C-MFA to generate a wild-type flux distribution for the metabolic network. Notably, flux elucidation through MFA alluded to serine generation via the mercaptopyruvate pathway. Using the elucidated flux distributions in conjunction with batch fermentation process yield data for various mutant strains, we constructed a kinetic model of C. thermocellum core metabolism (i.e. k-ctherm138). Subsequently, we used the parameterized kinetic model to explore the effect of removing substrate-level regulations on ethanol yield and titer. Upon exploring all possible simultaneous (up to four) regulation removals we identified combinations that lead to many-fold model predicted improvement in ethanol titer. In addition, by coupling a systematic method for identifying putative competitive inhibitory mechanisms using K-FIT kinetic parameterization with the ensemble-docking workflow, we flagged 67 putative substrate-level inhibition mechanisms across central carbon metabolism supported by both kinetic formalism and docking analysis.
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Joseph RC, Kelley SQ, Kim NM, Sandoval NR. Metabolic Engineering and the Synthetic Biology Toolbox for
Clostridium. Metab Eng 2021. [DOI: 10.1002/9783527823468.ch16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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12
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Strategies towards Reduction of Cellulases Consumption: Debottlenecking the Economics of Lignocellulosics Valorization Processes. POLYSACCHARIDES 2021. [DOI: 10.3390/polysaccharides2020020] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Lignocellulosic residues have been receiving growing interest as a promising source of polysaccharides, which can be converted into a variety of compounds, ranging from biofuels to bioplastics. Most of these can replace equivalent products traditionally originated from petroleum, hence representing an important environmental advantage. Lignocellulosic materials are theoretically unlimited, cheaper and may not compete with food crops. However, the conversion of these materials to simpler sugars usually requires cellulolytic enzymes. Being still associated with a high cost of production, cellulases are commonly considered as one of the main obstacles in the economic valorization of lignocellulosics. This work provides a brief overview of some of the most studied strategies that can allow an important reduction of cellulases consumption, hence improving the economy of lignocellulosics conversion. Cellulases recycling is initially discussed regarding the main processes to recover active enzymes and the most important factors that may affect enzyme recyclability. Similarly, the potential of enzyme immobilization is analyzed with a special focus on the contributions that some elements of the process can offer for prolonged times of operation and improved enzyme stability and robustness. Finally, the emergent concept of consolidated bioprocessing (CBP) is also described in the particular context of a potential reduction of cellulases consumption.
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Zhang W, Kang J, Wang C, Ping W, Ge J. Effects of pyruvate decarboxylase ( pdc1, pdc5) gene knockout on the production of metabolites in two haploid Saccharomyces cerevisiae strains. Prep Biochem Biotechnol 2021; 52:62-69. [PMID: 33881948 DOI: 10.1080/10826068.2021.1910958] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Saccharomyces cerevisiae has good reproductive ability in both haploid and diploid forms, a pyruvate decarboxylase plays an important role in S. cerevisiae cell metabolism. In this study, pdc1 and pdc5 double knockout strains of S. cerevisiae H14-02 (MATa type) and S. cerevisiae H5-02 (MATα type) were obtained by the Cre/loxP technique. The effects of the deletion of pdc1 and pdc5 on the metabolites of the two haploid S. cerevisiae strains were consistent. In S. cerevisiae H14-02, the ethanol conversion decreased by 30.19%, the conversion of glycerol increased by 40.005%, the concentration of acetic acid decreased by 43.54%, the concentration of acetoin increased by 12.79 times, and the activity of pyruvate decarboxylase decreased by 40.91% compared to those in the original H14 strain. The original S. cerevisiae haploid strain H14 produced a small amount of acetoin but produced very little 2,3-butanediol. However, S. cerevisiae H14-02 produced 1.420 ± 0.063 g/L 2,3-BD. This study not only provides strain selection for obtaining haploid strains with a high yield of 2,3-BD but also lays a foundation for haploid S. cerevisiae to be used as a new tool for genetic research and breeding programs.
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Affiliation(s)
- Wen Zhang
- Engineering Research Center of Agricultural Microbiology Technology, Ministry of Education, Heilongjiang University, Harbin, China.,Key Laboratory of Microbiology, College of Heilongjiang Province, School of Life Sciences, Heilongjiang University, Harbin, China
| | - Jie Kang
- Engineering Research Center of Agricultural Microbiology Technology, Ministry of Education, Heilongjiang University, Harbin, China.,Key Laboratory of Microbiology, College of Heilongjiang Province, School of Life Sciences, Heilongjiang University, Harbin, China
| | - Changli Wang
- Engineering Research Center of Agricultural Microbiology Technology, Ministry of Education, Heilongjiang University, Harbin, China.,Key Laboratory of Microbiology, College of Heilongjiang Province, School of Life Sciences, Heilongjiang University, Harbin, China
| | - Wenxiang Ping
- Engineering Research Center of Agricultural Microbiology Technology, Ministry of Education, Heilongjiang University, Harbin, China.,Key Laboratory of Microbiology, College of Heilongjiang Province, School of Life Sciences, Heilongjiang University, Harbin, China
| | - Jingping Ge
- Engineering Research Center of Agricultural Microbiology Technology, Ministry of Education, Heilongjiang University, Harbin, China.,Key Laboratory of Microbiology, College of Heilongjiang Province, School of Life Sciences, Heilongjiang University, Harbin, China
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14
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Bourgade B, Minton NP, Islam MA. Genetic and metabolic engineering challenges of C1-gas fermenting acetogenic chassis organisms. FEMS Microbiol Rev 2021; 45:fuab008. [PMID: 33595667 PMCID: PMC8351756 DOI: 10.1093/femsre/fuab008] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Accepted: 01/15/2021] [Indexed: 12/11/2022] Open
Abstract
Unabated mining and utilisation of petroleum and petroleum resources and their conversion to essential fuels and chemicals have drastic environmental consequences, contributing to global warming and climate change. In addition, fossil fuels are finite resources, with a fast-approaching shortage. Accordingly, research efforts are increasingly focusing on developing sustainable alternatives for chemicals and fuels production. In this context, bioprocesses, relying on microorganisms, have gained particular interest. For example, acetogens use the Wood-Ljungdahl pathway to grow on single carbon C1-gases (CO2 and CO) as their sole carbon source and produce valuable products such as acetate or ethanol. These autotrophs can, therefore, be exploited for large-scale fermentation processes to produce industrially relevant chemicals from abundant greenhouse gases. In addition, genetic tools have recently been developed to improve these chassis organisms through synthetic biology approaches. This review will focus on the challenges of genetically and metabolically modifying acetogens. It will first discuss the physical and biochemical obstacles complicating successful DNA transfer in these organisms. Current genetic tools developed for several acetogens, crucial for strain engineering to consolidate and expand their catalogue of products, will then be described. Recent tool applications for metabolic engineering purposes to allow redirection of metabolic fluxes or production of non-native compounds will lastly be covered.
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Affiliation(s)
- Barbara Bourgade
- Department of Chemical Engineering, Loughborough University, Loughborough, Leicestershire, LE11 3TU, UK
| | - Nigel P Minton
- BBSRC/EPSRC Synthetic Biology Research Centre (SBRC), School of Life Sciences, University Park, University of Nottingham, Nottingham, Nottinghamshire, NG7 2RD, UK
| | - M Ahsanul Islam
- Department of Chemical Engineering, Loughborough University, Loughborough, Leicestershire, LE11 3TU, UK
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15
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Srivastava RK, Akhtar N, Verma M, Imandi SB. Primary metabolites from overproducing microbial system using sustainable substrates. Biotechnol Appl Biochem 2020; 67:852-874. [PMID: 32294277 DOI: 10.1002/bab.1927] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2019] [Accepted: 04/12/2020] [Indexed: 02/06/2023]
Abstract
Primary (or secondary) metabolites are produced by animals, plants, or microbial cell systems either intracellularly or extracellularly. Production capabilities of microbial cell systems for many types of primary metabolites have been exploited at a commercial scale. But the high production cost of metabolites is a big challenge for most of the bioprocess industries and commercial production needs to be achieved. This issue can be solved to some extent by screening and developing the engineered microbial systems via reconstruction of the genome-scale metabolic model. The predicted genetic modification is applied for an increased flux in biosynthesis pathways toward the desired product. Wherein the resulting microbial strain is capable of converting a large amount of carbon substrate to the expected product with minimum by-product formation in the optimal operating conditions. Metabolic engineering efforts have also resulted in significant improvement of metabolite yields, depending on the nature of the products, microbial cell factory modification, and the types of substrate used. The objective of this review is to comprehend the state of art for the production of various primary metabolites by microbial strains system, focusing on the selection of efficient strain and genetic or pathway modifications, applied during strain engineering.
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Affiliation(s)
- Rajesh K Srivastava
- Department of Biotechnology, GIT, GITAM (Deemed to be University), Gandhi Nagar Campus, Rushikonda, Visakhapatnam, India
| | - Nasim Akhtar
- Department of Biotechnology, GIT, GITAM (Deemed to be University), Gandhi Nagar Campus, Rushikonda, Visakhapatnam, India
| | - Malkhey Verma
- Departments of Biochemistry and Microbial Sciences, Central University of Punjab, Bathinda, India
| | - Sarat Babu Imandi
- Department of Biotechnology, GIT, GITAM (Deemed to be University), Gandhi Nagar Campus, Rushikonda, Visakhapatnam, India
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16
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Ganguly J, Martin‐Pascual M, van Kranenburg R. CRISPR interference (CRISPRi) as transcriptional repression tool for Hungateiclostridium thermocellum DSM 1313. Microb Biotechnol 2020; 13:339-349. [PMID: 31802632 PMCID: PMC7017836 DOI: 10.1111/1751-7915.13516] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Revised: 11/06/2019] [Accepted: 11/12/2019] [Indexed: 01/13/2023] Open
Abstract
Hungateiclostridium thermocellum DSM 1313 has biotechnological potential as a whole-cell biocatalyst for ethanol production using lignocellulosic renewable sources. The full exploitation of H. thermocellum has been hampered due to the lack of simple and high-throughput genome engineering tools. Recently in our research group, a thermophilic bacterial CRISPR-Cas9-based system has been developed as a transcriptional suppression tool for regulation of gene expression. We applied ThermoCas9-based CRISPR interference (CRISPRi) to repress the H. thermocellum central metabolic lactate dehydrogenase (ldh) and phosphotransacetylase (pta) genes. The effects of repression on target genes were studied based on transcriptional expression and product formation. Single-guide RNA (sgRNA) under the control of native intergenic 16S/23S rRNA promoter from H. thermocellum directing the ThermodCas9 to the promoter region of both pta and ldh silencing transformants reduced expression up to 67% and 62% respectively. This resulted in 24% and 17% decrease in lactate and acetate production, correspondingly. Hence, the CRISPRi approach for H. thermocellum to downregulate metabolic genes can be used for remodelling of metabolic pathways without the requisite for genome engineering. These data established for the first time the feasibility of employing CRISPRi-mediated gene repression of metabolic genes in H. thermocellum DSM 1313.
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Affiliation(s)
| | - Maria Martin‐Pascual
- Laboratory of MicrobiologyWageningen UniversityStippeneng 46708WE WageningenThe Netherlands
| | - Richard van Kranenburg
- CorbionArkelsedijk 464206AC GorinchemThe Netherlands
- Laboratory of MicrobiologyWageningen UniversityStippeneng 46708WE WageningenThe Netherlands
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17
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Lee JW, Trinh CT. Towards renewable flavors, fragrances, and beyond. Curr Opin Biotechnol 2020; 61:168-180. [PMID: 31986468 DOI: 10.1016/j.copbio.2019.12.017] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2019] [Revised: 12/01/2019] [Accepted: 12/17/2019] [Indexed: 02/08/2023]
Abstract
Esters constitute a large space of unique molecules with broad range of applications as flavors, fragrances, pharmaceuticals, cosmetics, green solvents, and advanced biofuels. Global demand of natural esters in food, household cleaner, personal care, and perfume industries is increasing while the ester supply from natural sources has been limited. Development of novel microbial cell factories for ester production from renewable feedstocks can potentially provide an alternative and sustainable source of natural esters and hence help fulfill growing demand. Here, we highlight recent advances in microbial production of esters and provide perspectives for improving its economic feasibility. As the field matures, microbial ester production platforms will enable renewable and sustainable production of flavors and fragrances, and open new market opportunities beyond what nature can offer.
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Affiliation(s)
- Jong-Won Lee
- Bredesen Center for Interdisciplinary Research and Graduate Education, The University of Tennessee, Knoxville, TN, USA; Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Cong T Trinh
- Bredesen Center for Interdisciplinary Research and Graduate Education, The University of Tennessee, Knoxville, TN, USA; Department of Chemical and Biomolecular Engineering, The University of Tennessee, Knoxville, TN, USA; Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN, USA.
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18
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Sutiono S, Satzinger K, Pick A, Carsten J, Sieber V. To beat the heat - engineering of the most thermostable pyruvate decarboxylase to date. RSC Adv 2019; 9:29743-29746. [PMID: 35531508 PMCID: PMC9071941 DOI: 10.1039/c9ra06251c] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2019] [Accepted: 09/03/2019] [Indexed: 12/23/2022] Open
Abstract
Pyruvate decarboxylase (PDC) is a key enzyme for the production of ethanol at high temperatures and for cell-free butanol synthesis. Thermostable, organic solvent stable PDC was evolved from bacterial PDCs. The new variant shows >1500-fold-improved half-life at 75 °C and >5000-fold-increased half-life in the presence of 9 vol% butanol at 50 °C.
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Affiliation(s)
- Samuel Sutiono
- Chair of Chemistry of Biogenic Resources, Campus Straubing for Biotechnology and Sustainability, Technical University of Munich Schulgasse 16 94315 Straubing Germany
| | - Katharina Satzinger
- Chair of Chemistry of Biogenic Resources, Campus Straubing for Biotechnology and Sustainability, Technical University of Munich Schulgasse 16 94315 Straubing Germany
| | - André Pick
- Chair of Chemistry of Biogenic Resources, Campus Straubing for Biotechnology and Sustainability, Technical University of Munich Schulgasse 16 94315 Straubing Germany
| | - Jörg Carsten
- Chair of Chemistry of Biogenic Resources, Campus Straubing for Biotechnology and Sustainability, Technical University of Munich Schulgasse 16 94315 Straubing Germany
- Catalytic Research Center, Technical University of Munich Ernst-Otto-Fischer-Straße 1 85748 Garching Germany
| | - Volker Sieber
- Chair of Chemistry of Biogenic Resources, Campus Straubing for Biotechnology and Sustainability, Technical University of Munich Schulgasse 16 94315 Straubing Germany
- Catalytic Research Center, Technical University of Munich Ernst-Otto-Fischer-Straße 1 85748 Garching Germany
- Straubing Branch BioCat Fraunhofer IGB Schulgasse 11a 94315 Straubing Germany
- School of Chemistry and Molecular Biosciences, The University of Queensland 68 Copper Road St. Lucia 4072 Australia
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19
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Yamei, Guo YS, Zhu JJ, Xiao F, Hasiqimuge, Sun JP, Qian JP, Xu WL, Li CD, Guo L. Investigation of physicochemical composition and microbial communities in traditionally fermented vrum from Inner Mongolia. J Dairy Sci 2019; 102:8745-8755. [PMID: 31400900 DOI: 10.3168/jds.2019-16288] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2019] [Accepted: 06/13/2019] [Indexed: 12/26/2022]
Abstract
Mongolian traditionally fermented vrum is known for its functional characteristics, and indigenous microbial flora plays a critical role in its natural fermentation. However, studies of traditionally fermented vrum are still rare. In this study, we investigated the artisanal production of traditionally fermented vrum from Inner Mongolia. In general, its physicochemical composition was characterized by 34.5 ± 8% moisture, 44.9 ± 12.1% fat, 10.6 ± 3.2% protein, and 210 ± 102°T. The total lactic acid bacteria and yeast counts ranged from 50 to 2.8 × 108 cfu/g and from 0 to 1.1 × 106 cfu/g, respectively. We studied bacterial and fungal community structures in 9 fermented vrum; we identified 5 bacterial phyla represented by 11 genera (an average relative abundance >1%) and 8 species (>1%), and 3 fungal phyla represented by 8 genera (>1%) and 8 species (>1%). Relative abundance values showed that Lactococcus and Lactobacillus were the most common bacterial genera, and Dipodascus was the predominant fungal genus. This scientific investigation of the nutritional components, microbial counts, and community profiles in Mongolian traditionally fermented vrum could help to develop future functional biomaterials and probiotics.
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Affiliation(s)
- Yamei
- Xilingol Vocational College, Xilin Gol Institute of Bioengineering, Xilin Gol Food Testing and Risk Assessment Center, Xilinhot 026000, Inner Mongolia, China
| | - Yuan-Sheng Guo
- Xilingol Vocational College, Xilin Gol Institute of Bioengineering, Xilin Gol Food Testing and Risk Assessment Center, Xilinhot 026000, Inner Mongolia, China
| | - Jian-Jun Zhu
- Xilingol Vocational College, Xilin Gol Institute of Bioengineering, Xilin Gol Food Testing and Risk Assessment Center, Xilinhot 026000, Inner Mongolia, China
| | - Fang Xiao
- Xilingol Vocational College, Xilin Gol Institute of Bioengineering, Xilin Gol Food Testing and Risk Assessment Center, Xilinhot 026000, Inner Mongolia, China
| | - Hasiqimuge
- Xilingol Vocational College, Xilin Gol Institute of Bioengineering, Xilin Gol Food Testing and Risk Assessment Center, Xilinhot 026000, Inner Mongolia, China
| | - Jian-Ping Sun
- Xilingol Vocational College, Xilin Gol Institute of Bioengineering, Xilin Gol Food Testing and Risk Assessment Center, Xilinhot 026000, Inner Mongolia, China
| | - Jun-Ping Qian
- Xilingol Vocational College, Xilin Gol Institute of Bioengineering, Xilin Gol Food Testing and Risk Assessment Center, Xilinhot 026000, Inner Mongolia, China
| | - Wei-Liang Xu
- Xilingol Vocational College, Xilin Gol Institute of Bioengineering, Xilin Gol Food Testing and Risk Assessment Center, Xilinhot 026000, Inner Mongolia, China
| | - Chun-Dong Li
- Xilingol Vocational College, Xilin Gol Institute of Bioengineering, Xilin Gol Food Testing and Risk Assessment Center, Xilinhot 026000, Inner Mongolia, China
| | - Liang Guo
- Xilingol Vocational College, Xilin Gol Institute of Bioengineering, Xilin Gol Food Testing and Risk Assessment Center, Xilinhot 026000, Inner Mongolia, China.
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20
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Tian L, Conway PM, Cervenka ND, Cui J, Maloney M, Olson DG, Lynd LR. Metabolic engineering of Clostridium thermocellum for n-butanol production from cellulose. BIOTECHNOLOGY FOR BIOFUELS 2019; 12:186. [PMID: 31367231 PMCID: PMC6652007 DOI: 10.1186/s13068-019-1524-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 07/05/2019] [Indexed: 05/15/2023]
Abstract
BACKGROUND Biofuel production from plant cell walls offers the potential for sustainable and economically attractive alternatives to petroleum-based products. In particular, Clostridium thermocellum is a promising host for consolidated bioprocessing (CBP) because of its strong native ability to ferment cellulose. RESULTS We tested 12 different enzyme combinations to identify an n-butanol pathway with high titer and thermostability in C. thermocellum. The best producing strain contained the thiolase-hydroxybutyryl-CoA dehydrogenase-crotonase (Thl-Hbd-Crt) module from Thermoanaerobacter thermosaccharolyticum, the trans-enoyl-CoA reductase (Ter) enzyme from Spirochaeta thermophila and the butyraldehyde dehydrogenase and alcohol dehydrogenase (Bad-Bdh) module from Thermoanaerobacter sp. X514 and was able to produce 88 mg/L n-butanol. The key enzymes from this combination were further optimized by protein engineering. The Thl enzyme was engineered by introducing homologous mutations previously identified in Clostridium acetobutylicum. The Hbd and Ter enzymes were engineered for changes in cofactor specificity using the CSR-SALAD algorithm to guide the selection of mutations. The cofactor engineering of Hbd had the unexpected side effect of also increasing activity by 50-fold. CONCLUSIONS Here we report engineering C. thermocellum to produce n-butanol. Our initial pathway designs resulted in low levels (88 mg/L) of n-butanol production. By engineering the protein sequence of key enzymes in the pathway, we increased the n-butanol titer by 2.2-fold. We further increased n-butanol production by adding ethanol to the growth media. By combining all these improvements, the engineered strain was able to produce 357 mg/L of n-butanol from cellulose within 120 h.
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Affiliation(s)
- Liang Tian
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 USA
- Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
| | | | | | - Jingxuan Cui
- Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755 USA
| | - Marybeth Maloney
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 USA
- Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
| | - Daniel G. Olson
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 USA
- Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
| | - Lee R. Lynd
- Thayer School of Engineering, Dartmouth College, Hanover, NH 03755 USA
- Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37830 USA
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755 USA
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21
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Dash S, Olson DG, Joshua Chan SH, Amador-Noguez D, Lynd LR, Maranas CD. Thermodynamic analysis of the pathway for ethanol production from cellobiose in Clostridium thermocellum. Metab Eng 2019; 55:161-169. [PMID: 31220663 DOI: 10.1016/j.ymben.2019.06.006] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Revised: 06/01/2019] [Accepted: 06/14/2019] [Indexed: 12/17/2022]
Abstract
Clostridium thermocellum is a candidate for consolidated bioprocessing by carrying out both cellulose solubilization and fermentation. However, despite significant efforts the maximum ethanol titer achieved to date remains below industrially required targets. Several studies have analyzed the impact of increasing ethanol concentration on C. thermocellum's membrane properties, cofactor pool ratios, and altered enzyme regulation. In this study, we explore the extent to which thermodynamic equilibrium limits maximum ethanol titer. We used the max-min driving force (MDF) algorithm (Noor et al., 2014) to identify the range of allowable metabolite concentrations that maintain a negative free energy change for all reaction steps in the pathway from cellobiose to ethanol. To this end, we used a time-series metabolite concentration dataset to flag five reactions (phosphofructokinase (PFK), fructose bisphosphate aldolase (FBA), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), aldehyde dehydrogenase (ALDH) and alcohol dehydrogenase (ADH)) which become thermodynamic bottlenecks under high external ethanol concentrations. Thermodynamic analysis was also deployed in a prospective mode to evaluate genetic interventions which can improve pathway thermodynamics by generating minimal set of reactions or elementary flux modes (EFMs) which possess unique genetic variations while ensuring mass and redox balance with ethanol production. MDF evaluation of all generated (336) EFMs indicated that, i) pyruvate phosphate dikinase (PPDK) has a higher pathway MDF than the malate shunt alternative due to limiting CO2 concentrations under physiological conditions, and ii) NADPH-dependent glyceraldehyde-3-phosphate dehydrogenase (GAPN) can alleviate thermodynamic bottlenecks at high ethanol concentrations due to cofactor modification and reduction in ATP generation. The combination of ATP linked phosphofructokinase (PFK-ATP) and NADPH linked alcohol dehydrogenase (ADH-NADPH) with NADPH linked aldehyde dehydrogenase (ALDH-NADPH) or ferredoxin: NADP + oxidoreductase (NADPH-FNOR) emerges as the best intervention strategy for ethanol production that balances MDF improvements with ATP generation, and appears to functionally reproduce the pathway employed by the ethanologen Thermoanaerobacterium saccharolyticum. Expanding the list of measured intracellular metabolites and improving the quantification accuracy of measurements was found to improve the fidelity of pathway thermodynamics analysis in C. thermocellum. This study demonstrates even before addressing an organism's enzyme kinetics and allosteric regulations, pathway thermodynamics can flag pathway bottlenecks and identify testable strategies for enhancing pathway thermodynamic feasibility and function.
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Affiliation(s)
- Satyakam Dash
- Department of Chemical Engineering, The Pennsylvania State University, University Park, University Park, PA, USA; Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA.
| | - Daniel G Olson
- Thayer School of Engineering at Dartmouth College, Hanover, NH, USA; Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA.
| | - Siu Hung Joshua Chan
- Department of Chemical and Biological Engineering, Colorado State University, Fort Collins, CO, USA; Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA.
| | - Daniel Amador-Noguez
- Department of Bacteriology, University of Wisconsin, Madison, WI, USA; Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA.
| | - Lee R Lynd
- Thayer School of Engineering at Dartmouth College, Hanover, NH, USA; Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA.
| | - Costas D Maranas
- Department of Chemical Engineering, The Pennsylvania State University, University Park, University Park, PA, USA; Center for Bioenergy Innovation, Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA.
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22
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Engineering Clostridium for improved solvent production: recent progress and perspective. Appl Microbiol Biotechnol 2019; 103:5549-5566. [DOI: 10.1007/s00253-019-09916-7] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2019] [Revised: 05/15/2019] [Accepted: 05/15/2019] [Indexed: 01/07/2023]
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A mutation in the AdhE alcohol dehydrogenase of Clostridium thermocellum increases tolerance to several primary alcohols, including isobutanol, n-butanol and ethanol. Sci Rep 2019; 9:1736. [PMID: 30741948 PMCID: PMC6370804 DOI: 10.1038/s41598-018-37979-5] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Accepted: 12/17/2018] [Indexed: 01/17/2023] Open
Abstract
Clostridium thermocellum is a good candidate organism for producing cellulosic biofuels due to its native ability to ferment cellulose, however its maximum biofuel titer is limited by tolerance. Wild type C. thermocellum is inhibited by 5 g/L n-butanol. Using growth adaptation in a chemostat, we increased n-butanol tolerance to 15 g/L. We discovered that several tolerant strains had acquired a D494G mutation in the adhE gene. Re-introducing this mutation recapitulated the n-butanol tolerance phenotype. In addition, it increased tolerance to several other primary alcohols including isobutanol and ethanol. To confirm that adhE is the cause of inhibition by primary alcohols, we showed that deleting adhE also increases tolerance to several primary alcohols.
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Guo L, Ya M, Guo YS, Xu WL, Li CD, Sun JP, Zhu JJ, Qian JP. Study of bacterial and fungal community structures in traditional koumiss from Inner Mongolia. J Dairy Sci 2019; 102:1972-1984. [PMID: 30639001 DOI: 10.3168/jds.2018-15155] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Accepted: 11/09/2018] [Indexed: 11/19/2022]
Abstract
Koumiss is notable for its nutritional functions, and microorganisms in koumiss determine its versatility. In this study, the bacterial and fungal community structures in traditional koumiss from Inner Mongolia, China, were investigated. Our results demonstrated that 6 bacterial phyla represented by 126 genera and 49 species and 3 fungal phyla represented by 59 genera and 57 species were detected in 11 samples of artisanal koumiss. Among them, Lactobacillus was the predominant genus of bacterium, and Kluyveromyces and Saccharomyces dominated at the fungal genus level. In addition, there were no differences in the bacterial and fungal richness and diversity of koumiss from 3 neighboring administrative divisions in Inner Mongolia, and the bacterial and fungal community structures (the varieties and relative abundance of bacterial and fungal genera and species) were clearly distinct in individual samples. This study provides a comprehensive understanding of the bacterial and fungal population profiles and the predominant genus and species, which would be beneficial for screening, isolation, and culture of potential probiotics to simulate traditional fermentation of koumiss for industrial and standardized production in the future.
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Affiliation(s)
- Liang Guo
- Xilingol Vocational College, Xilin Gol Institute of Bioengineering, Xilin Gol Food Testing and Risk Assessment Center, Xilinhot 026000, Inner Mongolia, China.
| | - Mei Ya
- Xilingol Vocational College, Xilin Gol Institute of Bioengineering, Xilin Gol Food Testing and Risk Assessment Center, Xilinhot 026000, Inner Mongolia, China
| | - Yuan-Sheng Guo
- Xilingol Vocational College, Xilin Gol Institute of Bioengineering, Xilin Gol Food Testing and Risk Assessment Center, Xilinhot 026000, Inner Mongolia, China
| | - Wei-Liang Xu
- Xilingol Vocational College, Xilin Gol Institute of Bioengineering, Xilin Gol Food Testing and Risk Assessment Center, Xilinhot 026000, Inner Mongolia, China
| | - Chun-Dong Li
- Xilingol Vocational College, Xilin Gol Institute of Bioengineering, Xilin Gol Food Testing and Risk Assessment Center, Xilinhot 026000, Inner Mongolia, China
| | - Jian-Ping Sun
- Xilingol Vocational College, Xilin Gol Institute of Bioengineering, Xilin Gol Food Testing and Risk Assessment Center, Xilinhot 026000, Inner Mongolia, China
| | - Jian-Jun Zhu
- Xilingol Vocational College, Xilin Gol Institute of Bioengineering, Xilin Gol Food Testing and Risk Assessment Center, Xilinhot 026000, Inner Mongolia, China
| | - Jun-Ping Qian
- Xilingol Vocational College, Xilin Gol Institute of Bioengineering, Xilin Gol Food Testing and Risk Assessment Center, Xilinhot 026000, Inner Mongolia, China
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25
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Hon S, Holwerda EK, Worthen RS, Maloney MI, Tian L, Cui J, Lin PP, Lynd LR, Olson DG. Expressing the Thermoanaerobacterium saccharolyticum pforA in engineered Clostridium thermocellum improves ethanol production. BIOTECHNOLOGY FOR BIOFUELS 2018; 11:242. [PMID: 30202437 PMCID: PMC6125887 DOI: 10.1186/s13068-018-1245-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Accepted: 08/27/2018] [Indexed: 05/12/2023]
Abstract
BACKGROUND Clostridium thermocellum has been the subject of multiple metabolic engineering strategies to improve its ability to ferment cellulose to ethanol, with varying degrees of success. For ethanol production in C. thermocellum, the conversion of pyruvate to acetyl-CoA is catalyzed primarily by the pyruvate ferredoxin oxidoreductase (PFOR) pathway. Thermoanaerobacterium saccharolyticum, which was previously engineered to produce ethanol of high yield (> 80%) and titer (70 g/L), also uses a pyruvate ferredoxin oxidoreductase, pforA, for ethanol production. RESULTS Here, we introduced the T. saccharolyticum pforA and ferredoxin into C. thermocellum. The introduction of pforA resulted in significant improvements to ethanol yield and titer in C. thermocellum grown on 50 g/L of cellobiose, but only when four other T. saccharolyticum genes (adhA, nfnA, nfnB, and adhEG544D ) were also present. T. saccharolyticum ferredoxin did not have any observable impact on ethanol production. The improvement to ethanol production was sustained even when all annotated native C. thermocellum pfor genes were deleted. On high cellulose concentrations, the maximum ethanol titer achieved by this engineered C. thermocellum strain from 100 g/L Avicel was 25 g/L, compared to 22 g/L for the reference strain, LL1319 (adhA(Tsc)-nfnAB(Tsc)-adhEG544D (Tsc)) under similar conditions. In addition, we also observed that deletion of the C. thermocellum pfor4 results in a significant decrease in isobutanol production. CONCLUSIONS Here, we demonstrate that the pforA gene can improve ethanol production in C. thermocellum as part of the T. saccharolyticum pyruvate-to-ethanol pathway. In our previous strain, high-yield (~ 75% of theoretical) ethanol production could be achieved with at most 20 g/L substrate. In this strain, high-yield ethanol production can be achieved up to 50 g/L substrate. Furthermore, the introduction of pforA increased the maximum titer by 14%.
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Affiliation(s)
- Shuen Hon
- Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 USA
- Bioenergy Science Center, Oak Ridge National Laboratories, Oak Ridge, TN 37830 USA
- Center for Bioenergy Innovation, Oak Ridge National Laboratories, Oak Ridge, TN 37830 USA
| | - Evert K. Holwerda
- Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 USA
- Bioenergy Science Center, Oak Ridge National Laboratories, Oak Ridge, TN 37830 USA
- Center for Bioenergy Innovation, Oak Ridge National Laboratories, Oak Ridge, TN 37830 USA
| | - Robert S. Worthen
- Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 USA
- Bioenergy Science Center, Oak Ridge National Laboratories, Oak Ridge, TN 37830 USA
- Center for Bioenergy Innovation, Oak Ridge National Laboratories, Oak Ridge, TN 37830 USA
| | - Marybeth I. Maloney
- Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 USA
- Bioenergy Science Center, Oak Ridge National Laboratories, Oak Ridge, TN 37830 USA
- Center for Bioenergy Innovation, Oak Ridge National Laboratories, Oak Ridge, TN 37830 USA
| | - Liang Tian
- Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 USA
- Bioenergy Science Center, Oak Ridge National Laboratories, Oak Ridge, TN 37830 USA
- Center for Bioenergy Innovation, Oak Ridge National Laboratories, Oak Ridge, TN 37830 USA
| | - Jingxuan Cui
- Bioenergy Science Center, Oak Ridge National Laboratories, Oak Ridge, TN 37830 USA
- Center for Bioenergy Innovation, Oak Ridge National Laboratories, Oak Ridge, TN 37830 USA
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755 USA
| | - Paul P. Lin
- Bioenergy Science Center, Oak Ridge National Laboratories, Oak Ridge, TN 37830 USA
- University of California, Los Angeles, Los Angeles, CA 90095 USA
| | - Lee R. Lynd
- Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 USA
- Bioenergy Science Center, Oak Ridge National Laboratories, Oak Ridge, TN 37830 USA
- Center for Bioenergy Innovation, Oak Ridge National Laboratories, Oak Ridge, TN 37830 USA
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755 USA
| | - Daniel G. Olson
- Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 USA
- Bioenergy Science Center, Oak Ridge National Laboratories, Oak Ridge, TN 37830 USA
- Center for Bioenergy Innovation, Oak Ridge National Laboratories, Oak Ridge, TN 37830 USA
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Tian L, Perot SJ, Stevenson D, Jacobson T, Lanahan AA, Amador-Noguez D, Olson DG, Lynd LR. Metabolome analysis reveals a role for glyceraldehyde 3-phosphate dehydrogenase in the inhibition of C. thermocellum by ethanol. BIOTECHNOLOGY FOR BIOFUELS 2017; 10:276. [PMID: 29213320 PMCID: PMC5708176 DOI: 10.1186/s13068-017-0961-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 11/06/2017] [Indexed: 06/07/2023]
Abstract
BACKGROUND Clostridium thermocellum is a promising microorganism for conversion of cellulosic biomass to biofuel, without added enzymes; however, the low ethanol titer produced by strains developed thus far is an obstacle to industrial application. RESULTS Here, we analyzed changes in the relative concentration of intracellular metabolites in response to gradual addition of ethanol to growing cultures. For C. thermocellum, we observed that ethanol tolerance, in experiments with gradual ethanol addition, was twofold higher than previously observed in response to a stepwise increase in the ethanol concentration, and appears to be due to a mechanism other than mutation. As ethanol concentrations increased, we found accumulation of metabolites upstream of the glyceraldehyde 3-phosphate dehydrogenase (GAPDH) reaction and depletion of metabolites downstream of that reaction. This pattern was not observed in the more ethanol-tolerant organism Thermoanaerobacterium saccharolyticum. We hypothesize that the Gapdh enzyme may have different properties in the two organisms. Our hypothesis is supported by enzyme assays showing greater sensitivity of the C. thermocellum enzyme to high levels of NADH, and by the increase in ethanol tolerance and production when the T. saccharolyticum gapdh was expressed in C. thermocellum. CONCLUSIONS We have demonstrated that a metabolic bottleneck occurs at the GAPDH reaction when the growth of C. thermocellum is inhibited by high levels of ethanol. We then showed that this bottleneck could be relieved by expression of the gapdh gene from T. saccharolyticum. This enzyme is a promising target for future metabolic engineering work.
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Affiliation(s)
- Liang Tian
- Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 USA
- Bioenergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Skyler J. Perot
- Dartmouth College, Hanover, NH 03755 USA
- Bioenergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - David Stevenson
- Bioenergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- University of Wisconsin-Madison, Madison, WI 53706 USA
| | - Tyler Jacobson
- Bioenergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- University of Wisconsin-Madison, Madison, WI 53706 USA
| | - Anthony A. Lanahan
- Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 USA
- Bioenergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Daniel Amador-Noguez
- Bioenergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
- University of Wisconsin-Madison, Madison, WI 53706 USA
| | - Daniel G. Olson
- Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 USA
- Bioenergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
| | - Lee R. Lynd
- Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 USA
- Bioenergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN 37831 USA
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